The invention relates to a photoelectric position measuring device for measuring the position of two objects that are displaceable in relation to each other, and more particularly, a position measuring device having a scale embodied as a diffraction grating.
Positioning measuring devices having scales that are embodied as a diffraction grating are known, for example, from German Patent Publication No. DE 43 03 975 A1 and U.S. Pat. No. 5,424,833.
It is an object of the invention to disclose a high-resolution photoelectric measuring device, whose scanning signals have a high degree of modulation and which is simple to construct.
An advantage of the position measuring device according to the present invention lies in that the degree of modulation is still very good even when a light source having a low output power is used. The employment of a light source of low output has the advantage that heating of the entire measuring device is reduced thereby increasing measurement accuracy and long term stability of the device. Another advantage of the present invention resides in that the permissible tolerances of parameters, such as the light wavelength of the light source, the graduation period and bar-gap ratio, as well as the step height of the diffraction grating, are relatively large.
The invention will be explained in more detail by means of the drawings.